[Germ cells of the bird embryo: early localization, migration and colonization of gonadal anlagen].

Several experimental and morphological papers are analyzed concerning germ cell origin, migration and proliferation within sexually undifferentiated gonads. The germ material which is first localized in both anterior and posterior halves of the unincubated blastoderm assembles in the anterior area only at the beginning of incubation. In gonads the germinal population does not depend on the initial quantity of germ cells in the early blastoderm: its value seems to be determined by the somatic cells of the gonadal stroma. During the migratory phase, it is suggested that regulated interactions occur between the glycoconjugates of the moving germ cells and the physico-chemical characteristics of the extracellular matrices acting as substrates for the movement.